A patient was brought to casualty with seizures. He had multiple episodes and was taking herbal medicines for the same. He was conscious in between the episodes. During the episodes, he had arching of his back. What is the likely cause?

Correct Answer: D. Strychnine

Strychnine poisoning presents with characteristic opisthotonus (arching of the back), which is the pathognomonic clinical sign that distinguishes it from other plant toxin poisonings. Strychnine is a competitive antagonist of glycine receptors in the spinal cord, blocking the inhibitory neurotransmitter glycine. This removes spinal inhibition, leading to unopposed motor neuron firing and violent, sustained muscle contractions. The classic triad of strychnine poisoning includes: (1) seizure-like episodes with preserved consciousness between attacks, (2) opisthotonus and risus sardonicus (facial grimacing), and (3) muscle rigidity. The patient's history of taking herbal medicines is significant—strychnine contamination in traditional Indian herbal preparations (particularly those claiming to treat seizures or neurological conditions) is a documented source of poisoning. The conscious state between episodes is crucial; true epileptic seizures typically involve post-ictal confusion. Strychnine's effects are dose-dependent and can be rapidly fatal due to respiratory muscle paralysis. Management includes supportive care, benzodiazepines for muscle relaxation, and gastric decontamination if recent ingestion.

Why the other options are wrong

A. Ricinus — Ricinus communis (castor bean) toxicity presents with gastrointestinal symptoms (severe diarrhea, vomiting, abdominal pain) due to ricin, a protein toxin. It does not cause seizures or opisthotonus. The clinical picture is dominated by enteritis and fluid loss, not neuromuscular manifestations. This is a GI toxin, not a neurotoxin. B. Nerium odorum — Nerium odorum (oleander) poisoning causes cardiac arrhythmias, bradycardia, and GI symptoms due to cardiac glycosides. While it can cause CNS effects, it does not produce the characteristic opisthotonus or seizure-like episodes with preserved consciousness. Cardiac manifestations dominate the clinical picture, not neuromuscular rigidity. C. Datura — Datura species cause anticholinergic toxidrome: mydriasis, tachycardia, dry mouth, hyperthermia, and delirium ('mad as a hatter'). While seizures can occur, they are secondary to hyperthermia and metabolic derangement, not from direct spinal cord disinhibition. Datura does not produce opisthotonus or the characteristic muscle arching seen in strychnine poisoning.

High-Yield Facts

Mnemonics

STRYCHNINE = Spinal Toxin Rigidity Causes Hyperthermia, Opisthotonus, Neuromuscular Excitation Remember strychnine by its spinal site of action and the dramatic opisthotonus (back arching). Use this when you see 'arching of back' + 'conscious between episodes' in a toxicology question. OPISTHOTONUS = Strychnine's signature If the question mentions back arching or opisthotonus, think strychnine first. No other common plant poison causes this specific sign.

NBE Trap

NBE pairs herbal medicine use with seizures to lure students toward Datura (anticholinergic seizures) or Ricinus (GI toxin). The key discriminator is opisthotonus—only strychnine causes this pathognomonic sign due to spinal glycine receptor blockade.

Clinical Pearl

In Indian emergency departments, strychnine poisoning from contaminated herbal tonics (often sold as "brain tonics" or "seizure remedies") is an underrecognized cause of status epilepticus-like presentations. The key bedside clue is opisthotonus with clear sensorium between convulsions—a pattern that should immediately trigger toxicology screening and supportive care with benzodiazepines rather than antiepileptic drugs alone.

_Reference: Forensic Medicine & Toxicology (Reddy, 34th ed.) Ch. 24 (Plant Poisons); Parikh's Textbook of Medical Jurisprudence, Forensic Medicine & Toxicology Ch. 19_